Sulfonation of petroleum oils



2,815,370 Patented Dec. 3, 195'? SULFONATION or PETROLEUM olLs Le Roi E. Hutchings, Lakewood, and Gifi'ord W. Crosby, River Forest, Ill., assignors to The Pure Oil Company, Chicago, 111., a corporation of Ohio No Drawing. Application December 10, 1953, Serial No. 397,476

7 Claims. (Cl. 260504) This invention relates to a method of preparing sulfonates from hydrocarbon oils and more particularly to a method of preparing a basic sulfonate concentrate useful as an additive for lubricating oils.

Use of metal sulfonates as additives to impart detergency to lubricating oils is well known. Methods of pre paring metal sulfonates in situ in hydrocarbon oil in which the total sulfonation product is neutralized with a basic metal compound are disclosed in United States Patents Nos. 2,381,708 and 2,514,733. We have discovered that if a solvent extracted lubricating oil fraction, which has been subjected to light rather than drastic solvent refining, is sulfonated under proper conditions and the total sulfonation product neutralized with a large excess of base, the resulting product will be basic in character and eminently suited as a detergent concentrate for use in motor oil blends.

An object of this invention is to provide a method for preparing metal sulfonates in situ.

Another object of this invention is to increase the quantity of metal sulfonates which can be prepared from hydrocarbon oils.

A still further object of the invention is to provide a substantially sludge-free process for preparing sulfonates from hydrocarbon oils.

A further object of the invention is to provide a composition having a high detergent concentration.

Other objects will become manifest from the following description.

In accordance with our invention, we prefer to use as the oil to be sulfonated a Mid-Continent neutral oil fraction which has been solvent refined to a viscosity index of not more than about 90. Although stocks may be used which are more drastically refined, they give a lesser amount of sulfonate since most of the sulfonatable material is removed by the solvent refining process. Unrefined stocks or aromatic extracts produce considerable sludge which is difficult to maintain dispersed in the oil phase. In the event Pennsylvania base stocks are used, no refining prior to sulfonation is required to avoid the formation of considerable sludge. Where Gulf Coast or California base stocks of high naphthenicity are used, solvent refining can be carried to a higher degree than in the case of the Mid-Continent stocks. Any type of solvent refining designed to separate parafiinic and/or naphthenic hydrocarbons from aromatic hydrocarbons such as phenol, furfural, liquid sulfur dioxide and nitrobenzene extraction may be used to prepare the stock. Ordinarily, petroleum lubricating oil fractions, both neutrals and bright stock, having a viscosity from about 40 SSU to 200 SSU at 210 F. are suitable. In carrying out our invention, we prefer to dilute the petroleum stock with a suitable solvent prior to sulfonation in order to cut down the viscosity and facilitate sulfonation and also to assist in keeping the sludge in dissolved or dispersed condition. As solvent, we may use liquefied light paraffinichydrocarbons such as propane or butane; alkyl halides such as ethylene dichloride and amyl chloride;

nitroparaflins such as nitromethane and nitropentane, or other liquid which is a mutual solvent for the hydrocarbon and a sulfonating agent and inert to the sulfonating agent, particularly liquid sulfur dioxide. Although oleum or sulfur trioxide may be used as the sulfonating agent, we prefer to use sulfur trioxide diluted with a material inert to sulfur trioxide such as sulfur dioxide, nitrogen and/or ethylene chloride. Concentration of sulfur trioxide is preferably about 5% to 20% by weight. Air or oxygen may be charged With the sulfur trioxide in order to accelerate the sulfonation reaction. Contact between the oil and the sulfonating agent may be carried out in any suitable manner, as for example by mechanical or air agitation or.by countercurrent contact in a contacting tower filled with suitable contacting surfaces such as Raschig rings. Where sulfur trioxide in gaseous form is usedas a sulfonating agent, diluted sulfur trioxide is preferably countercurrently contacted with the hydrocarbon oil in a contacting tower.

Contact between the oil and the sulfonating agent is carried out at temperatures below 150 F. and preferably at a temperature of approximately 32 F. At temperatures above 150 F. undesirable reaction products form. At temperatures below about -20 F., the sulfonation reaction proceeds too slowly to be practicable. The ratio of sulfonating agent to oil will vary depending principally on the nature of the oil being treated. Oils which have a high content of aromatic hydrocarbons require higher ratios of sulfonating agent to oil to obtain complete sulfonation. In general, from 5 to parts by weight of sulfonating agent to 100 parts of oil undergoing treatment will produce a satisfactory concentrate. When using sulfur dioxide as a diluent in an operation in which gaseous sulfur trioxide is continuously recycled, we prefer to operate under sutficient superatmospheric pressure to dissolve enough sulfur dioxide in the organic liquid to avoid build up of sulfur dioxide in the recycle gas. The time of contact between the sulfonating agent and the oil may vary from approximately one minute to one hour depending upon the type of contact, the nature of the oil, and the sulfonating agent content. We have found that particularly good results are obtained if the oil to be sulfonated is mixed with an alkyl halide such asethylene chloride and liquid sulfur dioxide and contacted with sulfur trioxide at a sufliciently low tempera ture to maintain the sulfur trioxide in liquid phase.

As previously pointed out, one of the novel features of the invention is the use of a large excess of basic compound to neutralize the total sulfonation product, thereby not only obtaining a high concentration of sulfonate in the finished material, but enabling preparation of a sulfonate which is basic in character. In accordance with our invention, we use not less than 150% of base theoretically required to neutralize the acidity of the sulfonated oil and preferably between 150% and 300%. Neutralization is carried out at temperatures below 200 F. in order to prevent decomposition of the sulfonated products. Before neutralization, the sulfur dioxide present in the product i removed by vacuum distillation and/or gas stripping at a temperature below 150 F. After neutralization, other diluents, not reactable with the neutralizing agent, such as ethylene chloride, nitro-parafiins or paraffinic hydrocarbons, and any water formed in the reaction, are stripped from the product by heating it to a temperature of about 350 F. under vacuum with or without the aid of inert stripping gas such as nitrogen, superheated steam, or carbon monoxide. The stripped product is then filtered to remove solids such as unreacted base and inorganic salts.

I Asan' example illustrating the invention, 100 cc. of a Mid-Continent neutral oil having a viscosity index of and a viscosity of 200 SSU at F., prepared by sulfonates and other oil soluble reaction products.

extracting a wax distillate with phenol in a ratio of one part by weight of phenol to one part of distillate and then dewaxing by methyl ethyl ketone extraction, was diluted with 100 cc. of ethylene dichloride and 100 cc. of liquid sulfur dioxide. To this mixture was gradually added at 32 F., while stirring, a mixture consisting of 22 cc. of liquid sulfur dioxide, 22 cc. of ethylene dichloride and 10.7 grams of liquid sulfur trioxide. Mechanical agitation was continued for ten minutes, at the end of which time the product had a total acid number of 83.4, water-soluble acids totalling 43.5 acid number, and oil-soluble sulfonic acids totalling 40.9 acid number, measured in terms of milligrams of potassium hydroxide per gram of sulfonated oil. This product was vacuum stripped at temperatures below 150 F. to remove the sulfur dioxide and was then neutralized with solid barium hydroxide octahydrate in an amount equal to 300% of that theoretically required to neutralize the sulfonated product (based on total acid number). The barium hydroxide was in finely divided condition and agitation was continued until no further change in the basicity of the product occurred. After the neutralization was completed the ethylene dichloride and water were stripped by heating to 350 F. under vacuum and the resulting product was filtered to remove any solids. The product had a base number of 50.9, and the percent ash as sulfate (barium sulfate) was 24.5%, equivalent to 14.4% of barium in the product as barium petroleum It was determined that the final product, not counting the barium content, was equal to approximately 100% by weight of the oil sulfonated.

Another example, the same oil was sulfonated by passing sulfur trioxide gas into the oil for a period of two to three hours at a temperature of 150 F. at which time 0.087 gram of sulfur trioxide per gram of oil had reacted. The product was allowed to settle and the oil was decanted from the sludge. The oil and the sludge were each divided into two equal parts and one-half of the oil was recombined with one-half of the sludge. The combined oil and sludge were neutralized at room temperature with solid barium hydroxide octahydrate in an amount equal to 200% by weight of the amount theoretically required to neutralize the acidity of the combined product. The product was then heated to 350 F. for one-half hour.

The other half of the oil was likewise neutralized with solid barium hydroxide octahydrate in an amount equal to 200% by weight of the theoretical amount required. Ash, barium content, base number and acid number determinations were made on the two portions neutralized. The results are set forth in the following table:

1 Calculated from ash content taken as barium sulfate.

2 Considered to be substantially the same as sulfonic acid No.

From the results in Table I, it will be evident that the sulfonic acid content of the oil plus sludge is about 97% greater than the sulfonic acid content of the oil alone, and that the percent of barium present in the finished product in the form of oil soluble compounds, principally sulfonates, in the case of the oil plus sludge is about 75% greater than in the case of the oil alone.

The resulting product is useful per se as a lubricant or as an additive to incorporate the desired amount of barium or other metal or base in a soluble form in the finished oil.

In neutralizing the sulfonated reaction product, it is essential that a large excess of the basic compound be used. The usual practice of adding a small excess of basic compound in order to neutralize the acidity will not impart the desired basicity to the finished product.

The desirability and utility of the sulfonates prepared with a large excess of basic compound is indicated by bench detergency testing of sulfonates blended to the same barium content in a base oil. In this test, high detergency is indicated by a low deposit weight on a heated metal strip over which is circulated the oil containing a small amount of suspended carbon black. Sulfonates prepared by the use of -120% of the theoretical amount of barium hydroxide octahydrate for neutralization were faintly acidic or faintly basic. These materials were inferior in the bench detergency test to the basic sulfonates prepared by the use of 300% of the theoretical amount of barium hydroxide octahydrate for neutralization. Typical test data on sulfonates prepared by the sulfonation method outlined in the first example (basic barium sulfonate) compared with conventional neutral barium sulfonate are shown in Table II:

Table 11 Basic Neutral barium barium sulfonate sulfonate Base No., rngm., KOH/grn 25. 8 1. 3 Bench detergency test, mgm. of deposit 37 06 Instead of using solid barium hydroxide octahydrate for neutralization, other basic compounds such as sodium, potassium or lithium hydroxide and calcium, strontium, magnesium, or zinc or any combination thereof may be used for neutralization. Where it is desirable to obtain a combination of metal salts in the final product such as for example, calcium and zinc or barium and zinc, the basic compounds can be added in the desired proportions.

It will be seen, therefore, that not only have we succeeded in producing a high yield of sulfonated product from the oil, but we have succeeded in producing a high concentration of a basic salt in the finished product.

What we claim is: e

1. The method of preparing a sulfonate concentrate comprising sulfonating at a temperature between -20 F. and 150 F. with liquid sulfur trioxide a petroleum lubricating oil fraction having a viscosity between about 40 and 200 seconds Saybolt Universal at 210 F. and which has been solvent refined to a viscosity index not greater than about 90, in the presence of sufiicient mutual organic solvent for said fraction and said sulfur trioxide to assist in keeping sludge in dispersed condition, said solvent being substantially inert to sulfur trioxide under the conditions of sulfonation, removing any sulfur dioxide from the sulfonation product, then neutralizing the remaining total sulfonation product in the presence of said solvent with sufficient excess of basic metal compound not less than 150% of the theoretical amount necessary to neutralize the acidity of the sulfonation product to produce a product having a distinct basic reaction, and removing the solvent and any solid constituents from the finished product.

2. Method in accordance with claim 1 in which the solvent is an alkyl halide.

3. Method in accordance with claim 2 in which the solvent is ethylene dichloride.

4. Method in accordance with claim 1 in which the oil is a partially solvent refined neutral fraction.

5. Method in accordance with claim 1 in which the sulfonation is effected at about 32 F.

6. Method in accordance with claim 1 in which the basic compound is barium hydroxide octahydrate.

7. Method in accordance with claim 1 in which the sulfur'trioxide in liquid form is mixed with the solvent References Cited in the file of this patent UNITED STATES PATENTS Blumer Sept. 26, 1944 Arnott Aug. 7, 1945 6 Gn'esinger June 18, 1946 Cohen Dec. 31, 1946 Watkins et a]. Aug. 26, 1947 Fi'ncke Oct. 23, 1951 Eckert Sept. 16, 1952 Assefi et a1 Nov. 4, 1952 

1. THE METHOD OF PREPARING A SULFONATE CONCENTRATE COMPRISING SULFONATING AT A TEMPERATURE BETWEEN -20* F. AND 150*F. WITH LIQUID SULFUR TRIOXIDE A PETROLEUM LUBRICATING OIL FRACTION HAVING A VISVOSITY BETWEEN ABOUT 40 AND 200 SECONDS SAYBOLT UNIVERSAL AT 210*F. AND WHICH HAS BEEN SOLVENT REFINED TO A VISCOSITY INDEX NOT GREATER THAN ABOUT 90, IN THE PRESENCE OF SUFFICIENT MUTUAL ORGANIC SOLVENT FOR SAID FRACTION AND SAID SULFUR TRIOXIDE TO ASSIST IN KEEPING SLUDGE IN DISPERSED CONDITIONM SAID SOLVENT BEING SUBSTANTIALLY INERT TO SULFUR TRIOXIDE UNDER THE CONDITIONS OF SULFONTIONM REMOVING ANY SULFUR DIOXIDE FROM THE SULFONATION PRODUCT, THEN NEUTRALIZING THE REMAINING TOTAL SULFONATION PRODUCT IN THE PRESENCE OF SAID SOLVENT WITH SUFFICIENT EXCESS OF BASIC METL COMPOUND NOT LESS THAN 150% OF THE THEORETICAL AMOUNT NECESSARY TO NEUTRALIZE THE ACIDITY OF THE SULFONATION PRODUCT TO PRODUCE A PRODUCT HAVING A DISTINCT BASIC REACTION, AND REMOVING THE SOLVENT AND ANY SOLID CONSTITUENTS FROM THE FINISHED PRODUCT. 